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Avalanche Forecast

Archived

Dec 13th, 2022–Dec 14th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Moyie, St. Mary, Kokanee, Retallack, Valhalla.

We continue to receive reports of large natural and human-triggered avalanches on the persistent weak layer. Keep your terrain choices conservative and be prepared to back off quickly if you find signs of instability; whumpfing and shooting cracks.

Read our featured blog to learn more about how to manage a persistent slab problem when traveling in the backcountry.

Confidence

Moderate

Avalanche Summary

On Monday, several, size 2.5 natural persistent slab avalanches were observed in the Kaslo region. Explosives control throughout the Selkirks triggered size 2.5 avalanches on the mid-Niovember weak layer.

On Sunday, numerous surprise human-triggered avalanches were reported on the persistent weak layer between 2200 and 1700 m. The spookiest reports on this layer are of a skier remote avalanche, size 3, at Kokanee Glacier and a skier sympathetic avalanche, size 2.5 in the Kaslo region. These avalanches either failed on the November weak layers or 'stepped down' from a smaller avalanches onto these deeper instabilities.

Backcountry users throughout the region continue to report signs of instability: whumpfing and shooting cracks.

Snowpack Summary

5 - 10mm surface hoar is forming on a 30 - 40 cm soft slab. In the alpine snow has been redistributed by southerly winds into deep pockets. At treeline and below surface slab overlies a small layer of surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.

A weak layer of large surface hoar crystals, facets and a melt freeze crust sits 50-80 cm deep, buried in mid November. This layer has been very reactive at treeline between 1700-2200 m, on all aspects producing large remotely triggered avalanches. This layer will likely continue to be reactive through the week as northerly winds build wind slabs adding additional load to the weak layer.

Snowpack depths average 80-160 cm in the alpine.

Weather Summary

Tuesday Night

Mainly cloudy. Isolated flurries for the Purcells, trace accumulation. Northerly ridge wind 20 - 30 km/hr. Alpine temperatures, low of -10. Freezing levels valley bottom.

Wednesday

Sunny with cloudy periods. Isolated flurries for the Purcells, 2-5 cm accumulation. Northerly ridge wind 20 - 40 km/hr. Alpine temperatures, high of -6. Freezing levels valley bottom.

Thursday

Partly cloudy skies. Northwesterly ridge winds 20 - 30 km/hr. Alpine temperatures, high of -7. Freezing levels valley bottom.

Friday

Partly cloudy skies. Northwesterly ridge winds 40 - 60 km/hr. Alpine temperatures, high of -8. Freezing levels valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Avoid lee and cross-loaded slopes at and above treeline.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.